1. Field
The present invention relates to communications systems, and more specifically, to systems and techniques for controlling transmission power in a wireless communications system.
2. Background
Modern communications systems are designed to allow multiple users to access a common communications medium. Numerous multiple-access techniques are known in the art, such as time division multiple-access (TDMA), frequency division multiple-access (FDMA), space division multiple-access, polarization division multiple-access, code division multiple-access (CDMA), and other similar multi-access techniques. The multiple-access concept is a channel allocation methodology which allows multiple user access to a common communications link. The channel allocations can take on various forms depending on the specific multi-access technique. By way of example, in FDMA systems, the total frequency spectrum is divided into a number of smaller sub-bands and each user is given its own sub-band to access the communications link. Alternatively, in TDMA systems, each user is given the entire frequency spectrum during periodically recurring time slots. In CDMA systems, each user is given the entire frequency spectrum for all of the time but distinguishes its transmission through the use of a code.
In multi-access communications systems, techniques to reduce mutual interference between multiple users are often utilized to increase user capacity. By way of example, power control techniques can be employed to limit the transmission power of each user to that necessary to achieve a desired quality of service. This approach ensures that each user transmits only the minimum power necessary, but no higher, thereby making the smallest possible contribution to the total noise seen by other users. These power control techniques may become more complex in multi-access communications systems supporting users with multiple channel capability. In addition to limiting the transmission power of the user, the allocated power should be balanced between the multiple channels in a way that optimizes performance.
In one aspect of the present invention, a method of controlling transmission power includes receiving a first to second channel power ratio, adjusting the power ratio if a combined power of a plurality of channels exceeds a threshold, the channels including the first and second channels, and computing gain of the first channel as a function of the power ratio.
In another aspect of the present invention, a computer readable media embodying a method of controlling transmission receives a first to second power ratio, adjusts the power ratio if a combined power of a plurality of channels exceeds a threshold, the channels including the first and second channels, and computes gain of the first channel as a function of the power ratio.
In yet another aspect of the invention, an apparatus including a transmitter gain control configured to receive a first to second channel power ratio, adjust the power ratio if a combined power of a plurality of channels exceeds a threshold, the channels including the first and second channels, compute gain of the first channel as a function of the power ratio, and a transmitter configured to apply the computed gain to the first channel, combine the channels, and apply a second gain to the combined channels.
In a further aspect of the present invention, an apparatus includes means for receiving a first to second power ratio, means for adjusting the power ratio if a combined power of a plurality of channels exceeds a threshold, the channels including the first and second channels, and means for computing gain of the first channel as a function of the power ratio.
It is understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein is shown and described only exemplary embodiments of the invention, simply by way of illustration. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.